The present invention relates to a device for determining the wheel and/or axle geometry of motor vehicles in a measuring space, using an optical measuring device having at least two picture recording devices which, from at least two different perspectives, record a marking device including a plurality of wheel features arranged on a wheel, at least one vehicle body feature and a reference feature array having at least three reference features offset at least in one plane, and having an evaluation device, the position of the reference features in the measuring space being known in the evaluation device, the recording of the marking device taking place as the motor vehicle travels past, and the axis of rotation of a measured wheel being ascertained in the measuring space by simultaneous recording of the wheel features and of the at least one vehicle body feature at a plurality of points in time.
Such a device is known from German Patent No. DE 197 57 760 A1. Using several cameras, reference feature equipment and features or marks on the vehicle wheels and the vehicle body, the position of the wheel axles can be determined in a measuring space. The positioning of the reference features is known in the evaluation device. The evaluation uses the known methods of triangulation. This known examination method provides that the wheels shall travel past the measuring space. The camber of the wheel axles refers to the vertical line, and, provided this designated direction is known in a system of three-dimensional axes, it can be given for each wheel.
Things are different with the single toe of the wheels. The reference direction here lies in a plane perpendicular to the vertical, i.e. usually parallel to the floor of the test locale. The significant direction here is the travel axis, which is defined as the bisector of the single toes of the unsteered wheels.
Thus, for determining the single toes of the steered front wheels, it was customary up to now first to ascertain the travel axis by measuring the single toes of the rear wheels. Only then were the front wheels measured.
The present invention is based on the object of providing a device which yields a simpler determination of the wheel and/or axle geometry of motor vehicles using a simplified design.
According to the present invention, the vertical direction in the measuring space is determined from the position of the reference features in the measuring space, the direction of the travel axis of the motor vehicle is ascertained in the evaluation equipment on the basis of the recording by the marking device, separately for each wheel, from the path of motion of the at least one vehicle body feature, and the position of the axis of rotation of the wheel is determined with respect to the vertical direction and the direction of the travel axis.
Simply using these measures, the vertical direction and the direction of the travel axis are ascertained during passage of the vehicle, using a measuring device provided at one wheel, and from these, then, without measurements at further wheels, the data on the wheel and/or axle geometry of the respective wheel are obtained. Using the ascertained position of the wheel""s axis of rotation, it is easy to determine, for example, the camber as angle to the vertical and the single toe of the respective wheel as angle to the travel axis, without having to ascertain the travel axis as bisector of the nonsteered wheels.
The wheel axis can be determined exactly by obtaining the axis of rotation of the wheel during the passing of the vehicle by recording the individual rotary tracks of several wheel features, the translational motion of the motor vehicle, determined from the track of motion of the at least one vehicle body feature, being eliminated. From this one can calculate a rim runout compensation or compensate for the influence of similar disturbance variables. The exact plane of rotation of the wheel also becomes known from this.
The simple system is further favored by the fact that, for the purpose of ascertaining the vertical direction, the arrangement of the reference feature is suspended leveled out in a position at rest. If a plurality of reference features of the reference feature arrangement lie vertically above one another, the vertical direction can be determined particularly easily.
Changes in position of the vehicle with respect to the reference feature arrangement, which appear, for example, with steering angles for measuring and setting the axis geometry at the steered wheels or for ascertaining the position of the pivot pin, become noncritical because the direction of the axis of travel and/or the vertical direction are referred to a coordinate system related to the vehicle body, several vehicle body features being used for the parameter transformation. When the coordinate system related to the vehicle body is known, the change in position of the vehicle with respect to the reference feature arrangement does not take effect. A further advantageous development is that a test site for measuring of a steered wheel is provided, at which the measuring is done on the basis of the coordinate system related to the vehicle body.